Artificial slab



R. LATTORF ARTIFICIAL SLAB Filed Sept. 4, 1955 Jan. 11, 1938.

Patented Jan. 11, 1938 UNITED STATES ARTIFICIAL sLAB Richard Lattorf, Hanover, Germany, assignor to r The :United Limmerr and Vorwohle Rock Asphalte Company Limited, London, England,

aBritish company Application September 4, 1935, Serial No. 39,189-

V r In Germany April 13, 1934 I 2 Claims.

This invention relates to artificial stone slabs, such as are used for the paving of floors or other building purposes both inside and out of doors.

Known forms of slabs; composed of hydraulic mortar, are-often defective in that floors and pai ings made thereof are very cold for the feet. In addition such floors are very good sound conductors, and' when walked upon tend to rever berate the sound of the footsteps to a consider- 7 able extent. 7

I The object of the invention is to provide 'an artificial stone slab which shall-have a high insulating-capacity against transmission of heat and sound, and which may be rapidly'and cheaply "produced. a V

According to this invention there is provided an artificial stone slab, the upper or wearing surface of which is formed of granular natural stone with a matrix of hydraulic mortar, preferably of Portland cement mortar, united with an underlayer consisting of asphalt or of a mass containing asphalt. An artificial stoneslab in accordance with the invention is illustrated in the accompanying drawing. V

The invention moreover includes an artificial stone slab characterized in that the artificial stone mass contains filling materialsof granular rough texture, in order to ensure complete penetration into the asphalt mass and a good key therefor.

In this specification the term asphalt includes natural asphalt, or synthetic asphalt, or asphalt mastics;

In one embodiment of the invention the unification of the artificial stone mass and the asphalt underlayer is effected in a single operation under high compression of about seven thousand to eight and a half thousand pounds per square inch; the artificial stone mass is preferably applied with a minimum contentrof water, that is to say with a humidity approximating to that of soil.

The following description, given byway of example, shows'one way in which these slabs may 3 be made.

'In moulds, which are preferably situated on a rotating table, and which are open at'the top, there is first of all spread a layer of asphalt powder, suitably heated, to a thickness of about three-quarters to one inch. If. desired other ingredients may be mixed with the asphalt powder. The artificial stone is then spread on this layer to any desired thickness, preferably about threequarters of an inch to an inch and ahalf. The matrix of the said artificial stone is composed of hydraulic mortar, and preferably of Portland cement; if desired a high quality rapid hardening cement,e. g. the so-called rapid super hard cement, may be used. The filling material consists of an aggregate of a granular rough material such as natural stone chippings with a rough sharp surface, The artificial stone mass (consisting of a mixture of about one part cement and from one to three parts stone aggregate) is preferably used in a stiff doughy condition, i. c. with a minimum water content. It is therefore in a condition approximating to that of moist earth. Immediatelyupon the application and spreading of this artificial stone mass a high compression is exerted upon both layers. This com Dression amounts to about seven thousand to eight and a half thousand pounds per square inch. 7

Under the action of this high compression, the two layers are intimately combined and penetrate into one another at the point of contact.

. In a way the layers grow into oneanother inasmuch as the twomasses which are still plastic intimately combine during the application of the compression; and, since they penetrate into one another to a certain extent, there is no regular line of demarcation between the stone and the asphalt when a slab is seen in cross-section, but the line is of a broken character because at various points the respective layers have a greater or lesser penetration, thus affording an excellent key with each other. The excellence of this key is obviously to be ascribed to the use of the granular rough filling material in the artificial stone mass, and also to the plasticity and yielding quality of the compressed asphalt mass. This method of. manufacture produces a very durable composite slab and renders possible mass production on an economicaland rapid basis. 7

Although the underlayer is preferably composed of asphalt powder, it is also possible to manufacture the underlayer from mastic asphalt by casting, or from suitable masses having a considerable asphalt content. may suitably be composed of any natural mineral stone which has a granular rough texture.

The stone aggregate The foregoing description relates only to slabs has the advantage of being cheap and simple, and does not involve the use of expensive machinery,

The said filling material may consist of cork, asbestos, pumice, wood, peat and similar fibrous materials, and is intended to form an insulation against heat, cold and reverberation.

The following description, given by way of example, shows one method of making the slabs according to the above embodiment.

The hot asphalt is poured into moulds to a thickness of about three-quarters of an inch to one inch. Small pieces oi insulating materials of the kind above-mentioned are fixed in the asphalt before it is poured out. While it is in the moulds, and is still hot and comparatively liquid, dry grit is sprinkled upon it and combines therewith inseparably. This is done to provide a rough and unequal surface to afford a key for the artificial stone layer which is subsequently to be applied in a fairly liquid consistency.

After the cast asphalt has been cooled (either by air or by water), the artificial stone mortar mass is applied in a liquid consistency approximating to that of plaster, to a depth of about three quarters of an inch to an inch and a half.

The gritty and roughened surface of the cast asphalt underlayer gives an excellent key with the cement mortar mass, and when the latter has set it becomes inseparable from the underlayer. The surface of the artificial stone mass is smoothed off level with the top of the moulds before it has finally set hard.

Slabs constructed as above described afford excellent insulation both against extremes of temperature, moisture and reverberation. Owing to the elasticity of the asphalt underlayer increased breaking resistance is also obtained.

The surface of the artificial stone slab may obviously be finished in various ways; it may, for example, be tesselated, and may have various designs and/or colouring incorporated, and also a separate coating layer.

The lower face of the asphalt underlayer may be smooth, roughened or shaped in any desired manner.

The slabs themselves are laid in mortar in the normal manner.

What I claim and desire to secure by Letters Patent is:-

1. An artificial stone unit for building purposes comprising a layer of substantial thickness consisting of granular natural stone with a matrix of hydraulic mortar and a layer of substantial thickness of a mass containing asphalt, characterized in that the slab consists solely of the two layers united directly together so that the one layer is keyed or bonded into the other, the firstmentioned layer forming the wearing surface of the slab, while the asphalt-containing layer forms the base of the slab for attachment directly to the surface on which the slab is laid, at least a part of the particles of granular natural stone having a rough texture and being of sufiicient size to key the two layers together.

2. Tile covering, characterized by the fact that it is composed of a two-layer unit, the Wearing layer of which is of substantial thickness and is formed of granular natural stone with a matrix of hydraulic mortar united directly with an under layer of substantial thickness consisting of a mass containing asphalt, at least a part of the particles of granular natural stone having a rough texture and being of suflicient size to key the two layers together.

RICHARD LATTORF. 

